At present, with the rapid development of smart phones, the mobile internet is applied in every aspect of lives of people, and people pay more and more attention to information security. In view of this, the fingerprint recognition technology is developed rapidly and there is a great market demand for fingerprint recognition. The capacitance induction fingerprint recognition technology based on the semiconductor process is well developed, and people may detect fingerprint information via silicon sensors. A conventional fingerprint recognition unit circuit includes a detection electrode. An induction capacitance is generated between a surface of a finger and the detection electrode when the finger is placed over the detection electrode. There are concave portions and convex portions in a fingerprint on the surface of the finger, and a capacitance generated between a concave portion of a fingerprint and the detection electrode is different from a capacitance generated between a convex portion of the fingerprint and the detection electrode. The capacitance generated between the concave portion and the detection electrode is smaller than the capacitance generated between the convex portion and the detection electrode, so that the concave portion and the convex portion in the fingerprint can be determined and distinguished based on induction capacitances.
In addition, with the development of the low temperature poly-silicon (LTPS) technology, a fingerprint recognition method based on a glass substrate and the LTPS process is put forward. Moreover, the fingerprint recognition method based on a glass substrate and the LTPS process has a great cost advantage than a fingerprint recognition method based on the silicon process. Therefore, it is important to research the fingerprint recognition method based on a glass substrate and the LTPS process.
However, due to limitation factors in the LTPS process, there is a poor uniformity among threshold voltages (VTH) of thin film transistors (TFT). There may be a great difference between threshold voltages of thin film transistors at different positions on the same substrate, and there may also be a great difference between thin film transistors from different batches. For a conventional fingerprint recognition unit circuit, a difference between threshold voltages may result in a great difference in a recognition result, which makes it impossible to accurately determine concave portions and convex portions in the fingerprint, and it becomes difficult to perform fingerprint recognition on glass.